Apple has captured 59% of the U.S. smartphone sales at the top three carriers, versus 36% of smartphone sales a year prior, says Raymond James analyst Tavis McCourt, via Forbes.

In his note on the iPhone's dominance of top carriers, he says:

So, here’s a thought. Could it be the case that Google’s share of the smartphone market has peaked? That the phone-buying public simply is more inclined to choose Apple’s vertically integrated approach over the cacophony of the Android market? Could it, in fact, be the case that, while Google and Microsoft can innovate and find niche markets for their mobile OS offerings, that Apple has basically won the game, at least for the U.S. market? There’s no question that Android-based devices are crushing the likes of Nokia and Research in Motion at the low-end of the market, rapidly killing off the feature phone market. But at the top of the heap, Apple is crushing it. And iPhone 5 is just months away.

While Android fans will be quick to point out that smartphone sales happen outside the U.S., it's hard to see this as anything but a huge red flag for Android.

This very well could be the beginning of the end for Google's mobile operating system.

The fundamental problem for Google is that people prefer the iPhone to Android. No matter how you try to slice it, when you give a consumer the choice between an iOS device and an Android device, they are picking the iOS device.

We're seeing this play out in the smartphone market in the U.S. and we're seeing it play out globally in the tablet space. iPads are dominating. Android tablets are flopping.

So, unless Google can fix this problem and make Android a better operating system for consumers, it's going to find itself in a lot of trouble for a very long time.